1. FIELD OF THE INVENTION
This invention relates to siding. In particular, this invention relates to hardboard siding in which improved interlocking tongues and notches are provided for retaining adjacent panels in an overlapping relationship.
In each embodiment of the invention, the interlocking joint configuration of the panels insures that the nails which are utilized to secure the panels to an underlying material are covered by an overlapping marginal lower edge portion of an adjacent panel so that the nails are not exposed to the elements while simultaneously locking the lower marginal edge of the adjacent panel. The joint configurations also minimize the amount or percentage of panel surface which must be used to form the overlaying joints and provide for true horizontal alignment of each panel during installation.
2. History of the Related Art
Hardboard is a popular material for use in the manufacture of siding panels in the construction industry. Hardboard has been used to form siding panels for more than 20 years.
For the purposes of securing the siding to a building, it is customary to nail through an upper marginal edge portion of the lowest panel and then to apply the next panel so that it's lower marginal edge overlies the upper marginal edge of the previous panel and obscures the nails which have been driven through the previous nailed upper marginal edge. Thus, when a wall is completed, the only nails which are visible are those located along the upper marginal edge of the uppermost panel. It is customary to apply a cap or flashing in order to obscure these nails and to seal the upper end of the wall.
The problem with prior practices is that the lower marginal edge portion of each panel is free of attachment and consequently, the panels can lift under severe weather conditions or as a result of distortion of the panel resulting from severe climatic conditions or aging. The lifting problems can be easily overcome by merely nailing the lower marginal edge portions. However, if a nail is driven through the lower marginal edge portion, it is visible and is exposed to the elements. In practice in the industry, manufacturers have offered only a limited warranty with respect to their products when they are secured in position by exposed nails.
In order to prevent lifting of the lower marginal edge portion without the use of nails, the industry adopted the practice of inserting a plastic spline into the back face of each panel adjacent the lower edge thereof and providing a complementary locking tongue along the upper edge. This spline and tongue arrangement have been used in the industry for at least 15 years. In order to insert the spline, it is necessary to cut a deep groove in the back face of the panel and then it is necessary to drive an edge of the spline into the groove. This is a process which adds a substantial amount to the cost of manufacturing hardboard siding.
Despite the fact that the use of a spline in order to form a seat has been known to add a significant amount to the cost of producing hardboard siding, the industry has continued to use this spline construction for more than 15 years. In addition, despite the fact that it has been known to shape the upper edge of a hardboard siding panel in order to provide a tongue which can be inserted into the notch formed by the spline, no effort has been made to form a notch or seat capable of accommodating the locking tongue by forming the lower edge of hardboard panels to provide the seat.
In the present invention a locking seat is formed in the body of the siding panel which will adequately seat a locking tongue of an adjacent panel without requiring a separate spline.
Despite the fact that hardboard siding has a number of advantages over natural wood and in particular is not as prone to distortion when subjected to weathering, it is generally accepted care must be taken when shaping and forming hardboard to avoid reducing the thickness of the hardboard to an extent which will cause an edge of the board to break off.
When first considering replacing the seat formed between the spline and the back face of the panel with a seat formed in the body of the panel, knowledge of the accepted practices with respect to the machining of hardboard materials suggested that if a notch were made in the panel to a depth sufficient to provide a seat which would effectively retain a complementary tongue, it would weaken the lower marginal edge to such an extent as to make it fragile and not be capable of withstanding the rugged handling to which siding panels are subjected during shipping and installation. In addition, one of the essential characteristics of siding is that an adequate shadow line must be provided in order to create the desired esthetic finish associated with decorative siding. Therefore, if the thickness of the lower marginal edge portion were reduced, it was believed that the shadow which would be cast by the lower marginal edge portion would be reduced and this would adversely effect the esthetics of the finished product after installation. Surprisingly, it has been found that even if the width of the lower edge of the panel is reduced by 40% a perfectly satisfactory shadow line can be obtained.
Although a V-shaped notch is shown in the fibre insulation board units disclosed in U.S. Pat. No. 2,400,357, the characteristics of fibre insulation board are such that it would not have been obvious to those in the handboard siding industry that such a notch could be formed in an edge of a hardboard siding panel because of the reasons discussed above. The characteristics of hardboard are so dramatically different from those of fibreboard that the two materials are not considered as being interchangeable in the industry. A similar V-shaped notch is shown in the siding material disclosed in U.S. Pat. No. 2,231,007. Again, however, the siding material of the patent is a substantially thick material including an insulated base portion such as wallboard or layers of asphalt or cementitious compositions and a covering portion.
It would not be practical to make a siding panel from hardboard using a moulding process because such a process would be extremely expensive and moulding processes using hardboard generally involve the manufacture of hardboard panels in the conventional manner and subjecting the localized areas of the hardboard to additional compression in order to shape or contour the surface of the panel. It would not, however, be possible to compress a preformed hardboard panel to more than 10% of its preformed thickness and it would certainly be impossible to compress the panel by 40%. It would not therefore be practical to make a hardboard panel shaped to the configurations of the present invention using a moulding process applied to the hardboard.
A further problem encountered in various prior art siding materials is that the amount of material utilized to form the joint between adjacent panels is excessive thereby increasing the cost of the initial product. In U.S. Pat. No. 4,015,392 a siding system is disclosed which incorporates panels which have tongue and groove engaging portions which are spaced inwardly with respect to the upper end portion of the siding member. The nailing with regard to such panels is made in two spaced positions along the elongated upper end portion of each panel with the nails being covered by a portion of the overlying panel which is spaced remotely from the lower marginal edge of the overlapping panel. With this type of structure, approximately 10 to 20% of the effective width of each panel is consumed in providing the nailing surface which is spaced above each of the joints. This increases the effective cost of the material by the same 10 to 20%.
It has also been determined that there are difficulties inherit with installing hardboard siding incorporating tongue and groove structures in obtaining true horizontal alignment of each panel along the side of a given structure. In addition, other problems have been encountered due to the chemical treatment of the face of hardboard siding causing the siding to naturally assume a slight concave curvature when viewed from the front of each panel as the panel members are chemically treated. This places each of the panels in a somewhat curved stressed condition which can lead to fastener loosening over a period of time.
In additional example of a type of prior art siding material which incorporates simulated panels in a single panel structure is disclosed in U.S. Pat. No. 4,261,152.